Most yo-yos are in the form of two disk-shaped side portions that are rigidly connected to each other by some type of axle structure. The axle structure will normally include an elongated axle member that extends between the yo-yo's two side portions. In many modern yo-yos, the axle structure will also include a center-located bearing or other rotatable member that is positioned on said elongated axle member and forms an anchor for one end of a string-type tether. The free end of the tether is usually tied to create a loop portion that can be placed about one of a user's fingers to thereby secure the yo-yo to the user's hand.
When the tether is wound about the axle structure and the yo-yo is released or thrown from the user's hand, the yo-yo will begin to rapidly spin as it moves away from the user's hand and the tether unwinds from the axle structure. Once the tether is fully unwound, the yo-yo may “sleep” at the end of the tether, whereby the yo-yo continues to spin without the tether rewinding on the axle structure. Once the yo-yo is sleeping, there are a number of tricks, such as “walk the dog,” that a person can perform with the spinning yo-yo. A sleeping yo-yo is also often used to perform tricks where the spinning yo-yo is temporarily placed upon a portion of the tether intermediate of the tether's two ends.
At the completion of most yo-yo tricks, the user will make a quick tug/jerk on the tether. This will result in a brief tightening of the tether, which is then automatically followed by a temporary slackening of the tether. Once the tether goes slack, the tether's twist will cause one or more portions of the tether located proximate the axle structure to move, and thereby contact a spinning portion of the yo-yo. Once contact has occurred, the tether portion can become snagged on, or otherwise engaged to, a spinning portion of the yo-yo in a manner whereby rotation of the spinning portion of the yo-yo causes the tether to wind about the axle structure. Winding of the tether on the axle structure causes the yo-yo to return to the user's hand.
There are three crucial performance characteristics of a yo-yo that enable a user to perform yo-yo tricks. The yo-yo must be capable of sleeping for an extended period of time, it should return on command, and it should be smooth on the tether.
Concerning a yo-yo's sleep time, the longer the yo-yo can be made to sleep, the more time the user will have to complete any particular yo-yo trick that requires the use of a sleeping yo-yo. It is well known that by minimizing friction in the yo-yo's components, one can maximize the yo-yo's sleep time. Furthermore, it is known that whenever the tether even slightly rubs against a spinning portion of the yo-yo, the created friction will reduce the yo-yo's sleep time. Therefore, a yo-yo that has a large string gap will often sleep longer than a similar yo-yo having a smaller gap since the larger string gap reduces the chances of the tether contacting a spinning portion of the yo-yo. A yo-yo's string gap is herein defined as the area located between the yo-yo's two side portions. The string gap has a width dimension that is normally measured proximate the yo-yo's axle structure and extends from one of the yo-yo's side portions to the other of the yo-yo's side portions.
For a yo-yo to return on command, the structure and design of the yo-yo must be such that when the user causes the tether to briefly go slack, a portion of the tether can become snagged on and/or engage a spinning portion of the yo-yo and thereby cause the yo-yo to return to the user's hand. For this characteristic, one would want a small string gap, since a narrow gap requires a smaller sideways movement of the tether in order for said tether to contact a spinning portion of the yo-yo. However, a narrower gap facilitates inadvertent contact between the tether and a spinning portion of the yo-yo which could lead to the yo-yo returning to the user's hand without the user knowingly causing, or wanting, said return to occur. A yo-yo's responsiveness is hereby defined as the ease with which one can cause the yo-yo to return on command. A yo-yo that often inadvertently returns to the user's hand may be considered too responsive. A wide string gap is often a significant factor in a yo-yo that exhibits low responsiveness.
A yo-yo's responsiveness is usually enhanced through the use of particular engagement adaptations, such as raised ribs, on the tether-facing surface of the yo-yo's side portions. The tether-facing surface of a side portion is herein defined as the surface of the side portion that faces a portion of the yo-yo's tether when said tether extends outwardly from the yo-yo when said yo-yo is sleeping.
Concerning a yo-yo's ability to be smooth on the tether, this refers to a yo-yo's ability, when it is sleeping at the end of the tether, to be temporarily placed on a medial portion of the tether without the tether snagging on a spinning portion of the yo-yo. An example of a trick that requires a yo-yo to be smooth on the tether is “man on the trapeze.” If, during such a trick, the yo-yo can slide on the tether, the yo-yo is said to be very smooth on the tether/string. The ability of a yo-yo to be smooth on the tether is favored when the yo-yo's responsiveness is low, a condition usually associated with a wide string gap.
Another important consideration involved in the design/performance of a yo-yo is the wear rate of the yo-yo's tether and the portion(s) of the yo-yo that engage said tether. Wear occurs whenever the tether contacts a spinning portion of the yo-yo. A large string gap favors reduced wear.
The size of a yo-yo's string gap can also affect the yo-yo's dynamic characteristics when it is used to perform certain tricks. For example, a yo-yo having a wide string gap, where there is considerable distance between major portions of the yo-yo's two side portions, will tend to be more stable and easier to catch on a string. A yo-yo having a narrow string gap, where there is only a small spacing between major portions of the yo-yo's two side portions, will tend to be easier to use for performing looping tricks in which the yo-yo flips over when it passes the user's wrist.
It is known in the prior art to provide a yo-yo with structure that enables a user to adjust the size of the yo-yo's string gap. In such a yo-yo, to facilitate the performance of some tricks, one adjusts the yo-yo so that it has a narrow string gap. For other tricks, or if one wants to optimize the life of the yo-yo, the yo-yo is adjusted so that it has a wide string gap.
In most of the yo-yos that feature adjustable string gap, adjustment is accomplished via the yo-yo's axle structure. Both side portions are normally threadedly engaged to an elongated axle member whereby a user can rotate one of the side portions relative to the other side portion to thereby cause a change in the string gap. To prevent the side portions from inadvertently rotating relative to each other, it is known to employ one or more resilient o-rings on the axle member and/or employ one or more axle nuts that have a deformable portion and/or employ a detent-type locking apparatus secured to the axle member. However, repeated relative movements of the yo-yo's side portions can wear out such structures. Furthermore, such structures have limited strength to prevent inadvertent relative rotation between the side portions that could lead to changes in the yo-yo's string gap.
In U.S. Pat. No. 5,100,361, a yo-yo is taught in which a user can adjust the string gap by adjusting the position of gap screws that are located within cylindrical plugs secured into the center of disk-shaped wooden bodies. Adjustment of the screws is accomplished by taking the yo-yo apart, whereupon the user can employ a specially-shaped tool, or a fingernail, to turn said screws.
FIGS. 1 and 2 of the instant application show a prior art yo-yo 1, produced by Tom Kuhn Yo-Yos Ltd., that is functionally similar to the yo-yo shown in U.S. Pat. No. 5,100,361. However, in the yo-yo shown, each of the yo-yo's side portions 2 features a metal body 4 that has a center-located bore 6 that features interior threads 8. Each side portion further includes a gap screw 10 that has exterior threads 12 that engage the threads 8 of the body. Adjustment of the yo-yo's string gap is accomplished in the same manner and with the same tool as taught in U.S. Pat. No. 5,100,361. A user is required to disassemble the yo-yo and then rotate the gap screws to thereby cause the bodies to be closer or further apart when the yo-yo is reassembled.
However, the method of changing the string gap in the above-described yo-yo may require multiple repetitions of the adjustment process before the yo-yo exhibits the desired performance characteristics. Since said process requires the disassembly of the yo-yo for each adjustment of the gap screws, said process can be time consuming.
In addition, and most importantly, the prior art yo-yos that enable the string gap to be adjusted employ an adjustment apparatus that relies on a rotation of a part of the yo-yo wherein said rotation is about the same axis as the yo-yo's axis of rotation. As a result, when the yo-yo is rotating in its normal manner and the yo-yo returns to the user's hand, rotative forces can be created within the yo-yo that can act on the string gap adjustment apparatus and cause a change in the yo-yo's string gap. For example, when the yo-yo is returning to the user's hand, if the yo-yo hits the hand in a manner whereby both side portions of the yo-yo do not stop at the exact same time, there can be relative rotation of the side portions that will change the yo-yo's string gap.
Therefore, a yo-yo is needed in which the yo-yo's string gap can be easily, quickly, securely and precisely changed to meet the needs of the user. Furthermore, there is a need for a yo-yo in which the string gap can be adjusted and in which forces internally generated within the yo-yo will not inadvertently act to change the yo-yo's string gap.